HashMap自定义对象练习一（解法二） - 黑马程序员技术交流社区

import java.util.*;
//学生类
class Student implements Comparable<Student>
{
private String name;
private int age;
//构造函数初始化学生
Student(String name,int age)
{
this.name = name;
this.age = age;
}
public int compareTo(Student stu)
{
//按学生的年龄排序，如果年龄相等就按姓名字典序排序
int num = new Integer(this.getAge()).compareTo(new Integer(stu.getAge()));
if(num == 0)
return this.getName().compareTo(stu.getName());
//否则就按年龄排序
return num;
}
//计算学生对象的哈希地址
public int hashCode()
{
return name.hashCode()+age*37;
}
public boolean equals(Object obj)
{
//如果不是学生对象，抛出类型转换异常
if(!(obj instanceof Student))
throw new ClassCastException("不能转换成Student类型");
//类型转换
Student stu = (Student)obj;
//比较学生对象姓名和年龄，去除重复元素
return this.getName().equals(stu.getName()) && this.getAge()==stu.getAge();
}
public void setName(String name)
{
this.name =name;
}
public String getName()
{
return name;
}
public void setAge(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return name+"....."+age;
}
}
//主类用public修饰
public class MapTest
{
public static void sop(Object obj)
{
System.out.println(obj);
}
public static void main(String[] args)
{
//1 创建hashMap映射
HashMap<Student,String> hm = new HashMap<Student,String>();
//2 添加学生对象为键和对应的地址为值
hm.put(new Student("Jack",20),"北京");
hm.put(new Student("mike",19),"兰州");
hm.put(new Student("mike",19),"兰州");
hm.put(new Student("Tom",25),"广州");
hm.put(new Student("Alice",17),"上海");
hm.put(new Student("Jimmy",21),"长沙");
//3 取出学生和对应地址
getWay_2(hm);
}
//3.2 第二种方式从Map中取出所有键值
public static void getWay_2(HashMap<Student,String> hm)
{
sop("第二种方式从Map中取出所有键值");
//1 把所有的映射关系存入Set<Map.Entry<Student,String>>
Set<Map.Entry<Student,String>> entrySet = hm.entrySet();
//2 获取迭代器
for(Iterator<Map.Entry<Student,String>> it = entrySet.iterator(); it.hasNext(); )
{
//3 迭代取出映射项
Map.Entry<Student,String> me = it.next();
//4 获取学生
Student stu = me.getKey();
//5 获取地址
String addr = me.getValue();
//6打印获取结果
sop(stu.toString()+"......"+addr);
}
}
}

复制代码